Massachusetts Senator Edward Markey is asking for more information about the business practices of Herbalife, becoming the most prominent lawmaker to call for action after an activist hedge fund manager accused it of running a pyramid scheme. Herbalife shares tumbled 15 percent after Markey said Monday he had written to the U.S. Securities and Exchange Commission, the Federal Trade Commission and to Herbalife itself to try to obtain more information. The battle for the future of Herbalife has been raging for over a year after activist investor William Ackman accused the company of running a pyramid scheme, a charge the nutrition company vehemently denies.